The first step is to freeze your flank steak for about 30 minutes before you slice it. This will help you cut the steak easily but also evenly.
Now prep all of your other ingredients. Wash and cut your broccoli, mince your garlic and measure out all other ingredients. Set aside.
Lightly coat the inside of a slow cooker with oil and turn it on high. Grab your steak and slice it thin.
Add steak, beef broth, soy sauce, brown sugar, sesame oil, garlic, and chili flakes all to the slow cooker. Cover and cook on high for 2-3 hours or low 4-5 hours.
At about 2.5 hours, in a small bowl whisk together cornstarch and water until dissolved. Add that to the slow cooker and stir. Add your broccoli florets and cook another 10 minutes.
Serve over some rice or noodles and enjoy.
